1. Field of the Invention
The present invention relates in general to optical gate based optical space division switches, and more particularly to an optical space division switch in which optical gates are connected in a two-stage manner to cross-couple optical signals, so that optical signals inputted through arbitrary input ports can be switched to a desired output port with no internal collision.
2. Description of the Prior Art
Generally, optical gate based optical space division switches function to switch optical signals inputted through arbitrary input ports to a desired output port in response to optical gates being turned on or off.
A 4xc3x974 optical gate based optical space division switch has been proposed by Gustavsson et al., and it is shown in FIG. 1 herein (see: xe2x80x9cMonolithically integrated 4xc3x974 InGaAs/InP laser amplifier gate switch arraysxe2x80x9d, Electronic Letters, vol.28, no.24, pp.2223-2225, Nov. 1992).
As shown in FIG. 1, the 4xc3x974 optical gate based optical space division switch comprises an optical gate 110 with four optical amplifiers 111 based on semiconductor devices, and 1xc3x974 optical splitters 121-124 having their input terminals connected respectively to output terminals of the optical gate 110. Optical gates 131-134 each includes four optical amplifiers 111 based on semiconductor devices and has its input terminals connected respectively to output terminals of a corresponding one of the 1xc3x974 optical splitters 121-124. The conventional optical space division switch further comprises 4xc3x971 optical couplers 141-144 each having its input terminals connected respectively to corresponding ones of output terminals of the optical gates 131-134. An optical gate 150 includes four optical amplifiers 111 based on semiconductor devices, and has its input terminals connected respectively to output terminals of the 4xc3x971 optical couplers 141-144.
Noticeably, the input optical gate 110 and the output optical gate 150 are always maintained at their ON state. For this reason, the input and output optical gates 110 and 150 are not operated as optical gates for selectively transferring optical signals, but only as optical amplifiers for compensating for signal loss by optical components.
The operation of the conventional 4xc3x974 optical gate based optical space division switch with the above-mentioned construction will hereinafter be described.
First, the four optical amplifiers in the input optical gate 110 amplify optical signals inputted through input ports IP1-IP4 and transfer the amplified optical signals to the 1xc3x974 optical splitters 121-124, respectively.
Each of the 1xc3x974 optical splitters 121-124 splits a corresponding one of the output optical signals from the optical gate 110 into four optical signals and transfers the split optical signals to a corresponding one of the optical gates 131-134.
The four optical amplifiers in each of the optical gates 131-134 amplify the output optical signals from a corresponding one of the 1xc3x974 optical splitters 121-124 and transfer the amplified optical signals to the 4xc3x971 optical couplers 141-144, respectively. At this time, the optical gates 131-134 are turned on or off to selectively transfer the output optical signals from the 1xc3x974 optical splitters 121-124 to the 4xc3x971 optical couplers 141-144.
Each of the 4xc3x971 optical couplers 141-144 couples the four output optical signals from the optical gates 131-134 into one optical signal, which is then transferred to the output optical gate 150.
The four optical amplifiers in the output optical gate 150 amplify the output optical signals from the 4xc3x971 optical couplers 141-144 and transfer the amplified optical signals externally through output ports OP1-OP4, respectively.
However, the above-mentioned conventional optical sspace divisionswitch has a disadvantage in that, even if the optical gates 131-134 are turned off, they often transfer partially the optical signals due to their imperfect ON/OFF characteristic. Such crosstalk components degrade the performance of other signals.
Therefore, the present invention has been made in view of the above problem, and it is an object of the present invention to provide an optical gate based optical space division switch which is capable of switching optical signals inputted through arbitrary input ports to a desired output port with no internal collision. The transfer of the input optical signals is blocked by double gating so that they can hardly be transferred to undesired output ports. Hence, the input optical signals can be transferred only to a desired output port, resulting in a significant reduction in the number of their crosstalk components.
In accordance with one aspect of the present invention, there is provided an optical gate based optical space division switch for switching optical signals inputted through arbitrary input ports to a desired output port with no internal collision, comprising first splitting means for splitting the optical signals inputted through the input ports; first amplification means for selectively amplifying output optical signals from the first splitting means; second splitting means for splitting output optical signals from the first amplification means; second amplification means for selectively amplifying output optical signals from the second splitting means; coupling means for coupling output optical signals from the second amplification means; and third amplification means for amplifying an output optical signal from the coupling means and transferring the amplified optical signal to the output port.
In accordance with another aspect of the present invention, there is provided an optical gate based optical space division switch for switching optical signals inputted through arbitrary input ports to a desired output port with no internal collision, comprising first amplification means for amplifying the optical signals inputted through the input ports; signal splitting means for splitting output optical signals from the first amplification means; second amplification means for selectively amplifying output optical signals from the signal splitting means; first coupling means for coupling output optical signals from the second amplification means; third amplification means for selectively amplifying output optical signals from the first coupling means; and second coupling means for coupling output optical signals from the third amplification means and transferring the coupled result to the output port.